“They should be.” But the analyst confesses it is impossible to be sure.

“What’s it look like with a couple of Hellfires?” the decision maker asks, referring to smaller weapons carrying 20-pound warheads.

“If we hit the right room in the guesthouse, we’ll get the all bad guys.” But the walls of the house could be thick. The family’s safe, but bad guys might survive.

“Use the Hellfires the way you said,” the decision maker says.

Then a pause.

“Tell me again about these guys.”

“Sir, big A.Q. operators. We’ve been trying to track them forever. They’re really careful. They’ve been hard to find. They’re the first team.”

Another pause. A long one.

“Use the GBU. And that small building they sometimes use as a dorm …”

“Yes, sir.”

“After the GBU hits, if military-age males come out …”

“Yes, sir?”

“Kill them.”

Less than an hour later he is briefed again. The two targets are dead. The civilians have fled the compound. All are alive.

TARGETED killing using drones has become part of the American way of war. To do it legally and effectively requires detailed and accurate intelligence. It also requires some excruciatingly difficult decisions. The dialogue above, representative of many such missions, shows how hard the commanders and analysts work to get it right.

The longer they have gone on, however, the more controversial drone strikes have become. Critics assert that a high percentage of the people killed in drone strikes are civilians — a claim totally at odds with the intelligence I have reviewed — and that the strikes have turned the Muslim world against the United States, fueling terrorist recruitment. Political elites have joined in, complaining that intelligence agencies have gone too far — until they have felt in danger, when they have complained that the agencies did not go far enough.

The program is not perfect. No military program is. But here is the bottom line: It works. I think it fair to say that the targeted killing program has been the most precise and effective application of firepower in the history of armed conflict. It disrupted terrorist plots and reduced the original Qaeda organization along the Afghanistan-Pakistan border to a shell of its former self. And that was well before Osama bin Laden was killed in 2011.

Not many years before, the targeted killings were fairly limited. But by 2008, we knew that the terrorist threat had increased to intolerable levels, both to American forces in South Asia and to the United States itself. From our surveillance platforms, we could observe training camps where men leapt off motorbikes and fired on simulated targets. Early that year, the C.I.A. and I began recommending more aggressive action.

We were confident that the intelligence was good enough to sustain a campaign of very precise attacks. To be sure, it was not, is not, always error-free. In late 2006, for instance, a strike killed a one-legged man we believed was a chieftain in the Haqqani network, a violent and highly effective group allied with Al Qaeda and the Taliban. It turned out that the man was indeed affiliated with the Haqqanis, but he wasn’t the leader we wanted. With all the land mines in the region, there were many one-legged terrorists in South Asia.

I demanded a full explanation for the misidentification. There were no excuses. People were thoroughly, maybe even excessively, contrite.

But even if I was convinced that we could routinely provide high-quality intelligence to enable precision targeting, we still had to convince policy makers in the government that they should take advantage of it.

We had one thing going for us. I got to talk to President George W. Bush directly every week without filters. I briefed him every Thursday morning and began to use the sessions to underscore Al Qaeda’s growing footprint and brazenness in the tribal region of Pakistan. My chief analyst on this, a lanky Notre Dame graduate, met with me almost daily and stressed that as bad as this might be for Afghanistan and our forces there, the threat could also come to our shores.

If we had boiled our briefings down, the essence would have been: “Knowing what we know, there will be no explaining our inaction after the next attack.”

So the United States began to test some limits. In early 2008, a charismatic Qaeda operations chief was killed along the Afghanistan-Pakistan border. The strike was clean and the target so important that even regional reaction was muted. Local people knew who he was and did not mourn his passing.

Later in the year another senior Qaeda operative, active in planning attacks in the West, was killed along with several lieutenants in a similar strike that resulted in a similar reaction.

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CreditMike McQuade

By midsummer, when Hellfire missiles killed a senior Qaeda operator who was active in its weapons of mass destruction program, it was clear that the United States had launched a campaign of targeted killings in South Asia.

Publicly available sources document nearly three dozen attacks in the last seven months of the Bush administration, almost three times the total of the previous four years. According to those sources, 18 senior and midlevel Taliban and Qaeda leaders were killed.

The intelligence used for these strikes was based on human reports, surveillance technology and the near unblinking stare of the Predator itself. The strikes were particularly damaging to Al Qaeda’s operational leaders, who couldn’t afford to hunker down like Bin Laden and his deputy, Ayman al-Zawahri, whose main contribution to the movement was pretty much just staying alive. Those front-line operators had to move and communicate — and that made them vulnerable.

Other attacks were intended to disrupt known Qaeda locations and activities even when the identities of the people present were not known. Critics said these so-called signature strikes were indiscriminate. They were not. Intelligence for signature strikes always had multiple threads and deep history. The data was near encyclopedic.

Many such strikes killed high-value targets whose presence was suspected but not certain. And we made no excuses about killing lower-ranking terrorists. The United States viewed these attacks as legitimate acts of war against an armed enemy — and in warfare it is regrettably necessary to kill foot soldiers, too.

The signature strikes drastically shrank the enemy’s bench and made the leadership worry that they had no safe havens. Almost inadvertently, these strikes also helped protect intelligence sources and methods since the strikes seemed more random than they actually were.

It wasn’t long before intelligence reporting began to confirm our success. We learned there was a widespread sense of helplessness among the Qaeda leadership. Years later, documents proved just how anguished they were.

In 2015, an American court case against a Qaeda member prompted the government to release eight documents from the trove of Bin Laden letters captured when he was killed in Abbottabad, Pakistan, in 2011. Bin Laden’s correspondence with his chief lieutenants, in 2010, is remarkable in its candor.

The letters show the stress within the organization. “I convey my condolences regarding our great brother Sheikh Sa’id” who died “as a martyr during a spy plane attack,” read one from June 2010.

“The strikes by the spy planes are still going on,” it continued. A member named al-Sa’di Ihsanullah was the “latest to become a martyr: He was killed about a week ago, also by air raids.” It noted, “The midlevel commands and staff members are hurt by the killings.”

Signature strikes were also taking a toll. In November, the same Bin Laden lieutenant complained, after 20 fighters were killed in one place on Eid al-Fitr, the Muslim feast celebrating the end of Ramadan, that the men had “gathered for the holidays, despite our orders.”

Al Qaeda gained a healthy respect for American intelligence. “Based on our analysis, they are constantly monitoring several potential or possibly confirmed targets,” the June letter said.

The frightened underlings in the field beseeched Bin Laden to help. “We would like your guidance,” the June letter said. “Especially on this idea: reduce the work, meaning stopping many of the operations so we can move around less, and be less exposed to strikes.”

“There is an idea preferred by some brothers to avoid attrition,” it continued. “The idea is that some brothers will travel to some ‘safe’ areas with their families, just for protection. They would only stay for a time, until the crisis is over, maybe one or two years.”

Two months later another Bin Laden deputy agreed to their taking refuge and “calming down and minimizing movement.”

All this correspondence was from 2010, but it is consistent with the intelligence picture we were gathering in 2008. Al Qaeda along the Afghanistan-Pakistan border was spending more time worrying about its own survival than planning how to threaten ours.

The correspondence also confirmed our intelligence showing that attacking Americans on American soil was central to their plotting.

The letters are filled with references to recruits from a host of countries, including the United States. One correspondence emphasized that “operations inside America are some of the most important work of the Organization, as long as they are possible, because they affect the security and economy of the American people as a whole.”

Throughout the campaign, civilian casualties were a constant concern. In one strike, the grandson of the target was sleeping near him on a cot outside, trying to keep cool in the summer heat. The Hellfire missiles were directed so that their energy and fragments splayed away from him and toward his grandfather. They did, but not enough.

The target was hard to locate and people were risking their lives to find him. The United States took the shot. A child died, and we deeply regret that he did. But his grandfather had a garage full of dangerous chemicals, and he intended to use them, perhaps on Americans.

We tried to get better. Carefully reviewing video of one successful strike, we could discern — as a GBU was already hurtling toward an arms cache — a frightened woman responding to another weapon that had just detonated. She was running with young children square into the path of the incoming bomb, and they were killed. We realized, once our after-action review was done, that we needed to put even more eyes on targets as they were being struck to try to avoid any future civilian casualties.

For my part, the United States needs not only to maintain this capacity, but also to be willing to use it. Radical Islamism thrives in many corners of the world — Pakistan, Somalia, Yemen, Syria, Libya, Mali, the list goes on — where governments cannot or will not act. In some of these instances, the United States must.

And unmanned aerial vehicles carrying precision weapons and guided by powerful intelligence offer a proportional and discriminating response when response is necessary. Civilians have died, but in my firm opinion, the death toll from terrorist attacks would have been much higher if we had not taken action.

What we need here is a dial, not a switch.

Michael V. Hayden, a retired Air Force four-star general, was director of the Central Intelligence Agency from 2006 to 2009. He is the author of the forthcoming book, “Playing to the Edge: American Intelligence in the Age of Terror.”